Combination drag and rotary drilling bit



June 19, 1951 A. F. MAYDEW COMBINATION DRAG AND ROTARY DRILLING BITFiled Dec. 12, I947 INVENTOR. Aubrey McZJ dW Patented June 19, 1951COMBINATION DRAG AND ROTARY DRILLING BIT I Aubrey F. Maydew, SantaMaria, Calif.

Application December 12, 1947, Serial No. 791,353

1 Claim.

My present invention relates to the general class of rock drillingmachines for earth boring, and more specifically to an improved rotarydrilling bit of the drag type, employing multiple rotary, cutters, whichbit while adapted for various purposes and uses, is especially designedfor oilwell drilling operations in hard rock formations. Indrilling withthis, type of bit, if and when the gauge rollers or rotary cuttersbecome worn and reduced in diameter, the resulting bore or cylindricalhole is also reduced in diameter, and the undersize hole frequentlycauses the rotating bit to drag and wedge in the. bore, causing unduestrains and stresses on the drill pipe. Under these conditions asucceeding bit of full gauge and size is required to perform the addedfunction of reaming the reduced bore in order to reach the bottom of thebore for further drilling.

The primary object of my invention is the provision of means rigidlymounted on the rotating bit for maintaining a uniform gauge and forstabilizing and steadying the advancing bit against lateral drift. Thus,when using a rotary drilling bit with a twelve inch gauge, and equippedwith the cutters of my invention, the twelve inch diameter of thecylindrical bore is uniformly maintained throughout the depth of thewell, and a straight vertical bore or hole is formed.

For this purpose the bit is equipped with additional cutting meansacting as a pilot cutter adapted to cut a central socket for the bit inthe advancing bottom of the bore, together with a pair of rigid cuttersadapted for forming an annular groove in the bottom of the hole forstabilizing and steadying the advancing bit.

The resulting pattern on the bottom of the bore includes a right conewith a central hole or socket and a surrounding annular gauge groove.

The auxiliary cutting means includes a minimum number of parts that maywith facility and low cost of production be manufactured, and assembledwith convenience on the bit or a unitary supporting structure of thebit, to insure durable and eflicient tool for the purposes desired. Theinvention consists in certain novel features of construction andcombinations and arrangements of parts as will hereinafter be describedand particularly pointed out in the appended claim. In the accompanyingdrawings I have illustrated a complete example of a physical embodimentof my invention wherein the parts are combined and arranged in accordwith one mode I have devised for the practical application of theprinciples of my invention. It will however, be understood that variouschanges and alterations are contemplated and may be made in theseexemplifying drawings and mechanical struc-- tures, within the scope ofmy claim, without departing fromthe principles'of the invention, as isevidenced by the modified forms of the invention illustrated in thedrawings.

Figure l is a view in elevation of a rotary bit having multiple rotarycutters and equipped with the auxiliary cutters or abrading devices ofmy invention; and Figure 2 is a similar view as seen from the right orleft of Fig. 1.

Figure 3 is a bottom plan view of the bit.

Figure 4 is a detailview partly in section ShOWm.

ing one of the auxiliary gauging devices as a hard metal stud or blade.

Figure 5 is a sectional detail view of the central pilot or abradant forforming the socket in the bottom of the bore; and Figure 6 is a faceview of this cutter.

Figure 7 shows a lateral face view of an abrading cutter with diamondinserts.

In the assembly views of the drawings I have illustrated a conventionaltype of rotary bit having an upper threaded stud I for attachment to thedrill rod or pipe of a well drilling appliance; and this stud forms anintegral part of a forged steel structure that includes fourdiametrically arranged outwardly or laterally spaced arms arranged inopposed pairs for use in supporting the multiple rollers or rotarycutters of the bit. Two short opposed bearing arms 2, 2, are arrangeddiametrically of the two longer gauging arms 3, 3, that also areutilized as bearings, and the four arms are forged integrally with auniting cross bar or bridge 4.

Between the respective arms 2, 2, and the bridge suitable rotarycutters, as 5, 5, are located and journaled; and between the opposedgauge arms 3, 3, and the bridge two gauging cutters 6, 6, are locatedand journaled. These multiple rotary cutters may be of different sizesand shapes as desired, and as here illustrated the staggered and steppedcutters are designed to fashion a pattern on the bottom of the boresimulating a right cone.

By the use of the auxiliary cutters of my invention the conical bottomis fashioned with a central cylindrical socket and a surrounding annulargauge groove, both of predetermined depth and width.

For cutting the central pilot socket a short blade or stud 1 of hardenedsteel is shown in Figures 2 and 3 and to form the gauge groove the twogauge arms 3, 3, are equipped with similar short blades or studs 8 and9. The cutting blade or stud 1 is welded to the bridge, and the bladesor studs 8 and 9 are welded to the gauge arms rigid with the frame ofthe bit project downwardly in advance of the multiple rotary cutters, toform the pattern in the bottom of the bore, and the two gauge cutters 8and 9 form the annular groove in the pattern with the outer wall of thegroove the exact gauge or diameter corresponding to the gauge of thebit. The pilot cutter 1 which forms the guide socket in the pattern isof predetermined depth and width to fashion the desired socket; andthese three cutters work in advance of the main rotary cutters of thebit.

In Figs. 5 and 6 a modified form of pilot cutter is illustrated wherethe solid cylindrical stud ll, united as by welding, or integral with,the bridge. is provided with a central socket to accommodate a diamondinsert l2 that cooperates with a series of radiating teeth [3surrounding the dia mond insert, and this composite cutter rigid withand rotating with the bit produces the pilot socket in the pattern.

. In Fig. 7 a further modified form of auxiliary cutter, which cuts andabrades the hard rock similar to the auxiliary cutter in Figs. 5 and 6,is provided on the beveled blade or stud l4, and the abrading diamondinserts 15 are rigidly mounted in the beveled edge l6. These compositecutting and abrading auxiliary devices are adapted for use in variousrock formations, and the auxiliary cutters, as well as the main rotarycutters, of the bit may be interchanged as desired to meet varyingconditions in earth boring.

Having thus fully described my invention, what I claim as new and desireto secure by Letters Patent is:

The combination with a rotary drill bit having a pair of spaced gaugearms and a central bridge supported between and on the gauge arms,multiple rotary cutters journaled between the arms and the bridge, andopposed bearing arms supporting the rotary cutters, of a pair of gaugingcutters projecting forwardly from said arms for forming a gauge groovein advance of the bit, a central stud on the bridge projecting inadvance of the bit, said stud having a central socket, a central diamondinsert in the socket in the stud, and a series of radiating cutter teethon the lower edge of the stud surrounding said insert.

AUBREY F. MAYDEW.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 122,514 Bullock 1 Jan. 9, 1872458,640 Phillips Sept. 1, 1891 1,299,619 Rose 1 1 Apr. 8, 1919 1,348,419Hughes Aug. 3, 1920 1,865,853 Granville July 5, 1932 2,034,073 Wright 11Mar. 17, 1936 2,053,801 Mitchell 11 Sept. 8, 1936 2,121,202 KillgoreJune 21, 1938 2,198,849 Waxler Apr. 30, 1940

